Cardioversion timing and ventricular rate control in atrial fibrillation
THE CONTEXT
Restoring and maintaining sinus rhythm is most successful in younger patients with atrial fibrillation (AF) lasting less than 3 months and no important structural heart disease.
Restoring and maintaining sinus rhythm
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Immediate cardioversion can be considered when AF has lasted less than 24 hours.
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In stable patients without structural heart disease, intravenous flecainide at 2 mg/kg over 30 minutes, up to 150 mg, restores sinus rhythm in 75% within 8 hours.
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Intravenous amiodarone through a central venous catheter can be used in structural or ischaemic heart disease. DC cardioversion requires deep sedation or general anaesthesia.
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When AF has lasted at least 24 hours or its duration is uncertain, defer cardioversion until effective oral anticoagulation has been established for at least 3 weeks and underlying problems have been corrected.
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Prophylactic amiodarone reduces recurrence. Catheter ablation can maintain sinus rhythm in persistent AF, but is less successful than in paroxysmal AF.
Rate control
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If sinus rhythm cannot be restored, direct treatment towards heart rate control.
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Beta-blockers, verapamil, diltiazem and digoxin reduce ventricular rate by slowing atrioventricular (AV) conduction. Rate reduction alone may markedly improve cardiac function, particularly in mitral stenosis.
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Beta-blockers and rate-limiting calcium antagonists control exercise heart rate more effectively than digoxin and offer additional benefits in hypertension or structural heart disease.
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Digoxin can be combined with a beta-blocker. Calcium channel antagonists should not be combined with beta-blockers because of bradycardia risk.
Pace and ablate
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Exceptional cases of poorly controlled, symptomatic AF can be treated by permanent pacemaker implantation followed by catheter ablation deliberately producing complete AV nodal block.